In an internal combustion engine, ancillary devices may be provided, such as water pumps, power steering, etc. The ancillary devices may be driven off the crankshaft at the same speed as the engine. Thus, the ancillary devices have a predetermined gearing in order to fulfill a maximum load. Further, the ancillaries may be driven faster than a load demand, which may result in reduced fuel economy for the engine.
Other attempts to address running ancillary devices include using one or more independent electric motors to drive the ancillary devices at variable speeds such that the ancillary device may operate at a speed appropriate to a load demand. Another attempt to address running ancillary devices include using a variable speed drive, such as a gearbox, that is driven mechanically by the output shaft of the main drive motor and is coupled to the ancillary device.
However, the inventors herein have recognized potential issues with such systems. In the first approach, the power to drive the ancillary devices using electric motors may result in losses due to the generation, storage, and motor cycle of the independent electric motors. In the second approach, standard gearboxes may provide discrete gear ratios and therefore be unable to provide a fully variable speed drive to the ancillary device.
One potential approach to at least partially address some of the above issues includes a system and method for an electrical machine for driving one or more ancillary devices of a motor. The electrical machine may comprise a stator, which is configured to be rotated, and a rotor, which is rotatably mounted relative to the stator. The rotational speed of the rotor of the electrical machine depends upon a supply current to the electrical machine and the rotational speed of the stator.
For example, an ancillary device, such as an alternator, may be driven at a lower speed when the load on the motor's starter battery system is low or at a higher speed when the load is high. In another example, a speed of the ancillary device of the coolant system of the motor may vary continuously depending on the motor operation and/or the ambient conditions.
In this way, the ancillary devices may be driven at speeds appropriate to the operating conditions of the motor. Thus, the ancillary devices being driven at appropriate speeds may improve fuel economy and/or improve motor performance.
Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be carried out by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described actions, operations and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the engine control system, where the described actions are carried out by executing the instructions in a system including the various engine hardware components in combination with the electronic controller.